1. Field
Example embodiments of the present patent application generally relate to an image forming apparatus and a recording medium conveying device included in the image forming apparatus, for example, to an image forming apparatus and a recording medium conveying device used in the image forming apparatus, in which a dog ear formed on a recording medium and/or skew of a recording medium may effectively be detected during a transfer operation of the recording medium.
2. Discussion of the Related Art
Related-art image forming apparatuses and recording medium conveying devices form an image on a recording medium or transfer a recording medium according to a condition of the recording medium conveyed therein.
Such a related-art image forming apparatus includes a configuration in which a transfer deviation sensor detects a position of the edge of a recording medium or recording paper across a sheet width direction perpendicular to a sheet travel direction of the recording medium or recording paper. This sensor detects the position of the edge of a recording medium across the sheet width direction and obtains an amount of sheet transfer deviation of a recording medium so that the related-art image forming apparatus may form an image at a correct position on the recording medium, based on the detection results obtained as described above.
Such a related-art image forming apparatus may alternatively employ a configuration in which a deviation sensor detects at least two positions of the edge of a recording medium and a controller determines whether the recording medium has skew or not by referring to the detected positions. Based on the above-described determination results, the controller displays an error message. The related-art image forming apparatus with this configuration determines whether a recording medium is skewed or not, and adjusts an image according to the degree of skew of the recording medium to form the image at an accurate position on the recording medium. By so doing, even when a recording medium is conveyed obliquely in the sheet travel direction, an image may be properly formed at an appropriate position on the recording medium, thereby avoiding production of a defect copy. In addition, depending on the degree of skew of a recording medium, the controller causes an operation panel or other display unit to display an error message to notify a user of the failure and/or causes a transfer operation of the recording medium to stop. With the above-described operations, a paper jam caused by the skew of the recording medium may be prevented.
Another drawback causing defects or damages during an image forming operation with respect to a recording medium is that a corner or corners of the leading or trailing edge or both edges of a recording medium may be folded down during the transfer operation. Such a folded corner of a recording medium or recording paper is called and referred hereinafter to as a “dog ear.”
Compared with a recording medium having no dog ear, a recording medium having a dog ear may easily be caught in a material forming a conveying path of the recording medium, and therefore, the recording medium may easily get jammed in the conveying path. Depending on a user, the dog ear itself is regarded as a failure when found on a recording medium with an image formed thereon.
A demand for avoiding failures due to dog ear(s) of a recording medium is increasing as well as a demand for higher accuracy in image forming position. For example, when a printout page has a dog ear or dog ears when binding the printouts as a book, the entire book may be regarded as a defective product.
Such a recording medium or printout having a dog ear therein has been removed by a user manually or by hand prior to the binding operation or the entire book or set of printouts including such a recording medium has been printed again. This may impose a great load and loss to a user or manufacturer.
Further, when an extremely large dog ear has been made, a paper jam may occur in an image forming apparatus. When a paper jam occurs due to such a large dog ear, the recording medium may be bent or folded in a complex manner. Therefore, a load on a user may increase when removing such a jammed recording medium from the image forming apparatus.
Furthermore, if a user finds it difficult to remove the jammed paper by himself or herself, the user may contact a maintenance person. Accordingly, a downtime period of the image forming apparatus increases, which reduces the production of the image forming apparatus.
Accordingly, the above-described actions may cause a waste of time and unnecessary load on a user, as well as a waste of paper resources and energy to drive the image forming apparatus.